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Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques

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Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques ISSN: 2574-1241 Volume 5- Issue 4: 2018 DOI: 10.26717/BJSTR.2018.10.001930 Koray Ak. Biomed J Sci & Tech Res Review Article Open Access Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques Koray Ak* Department of Cardiovascular Surgery, Marmara University School of Medicive, Turkey Received: Published: *Corresponding: September author: 29, 2018; : October 23, 2018 Koray Ak, Kalp ve Damar Cerrahisi AD, Sağlık Bakanlığı Marmara Universitesi, Pendik Egitim ve Arastirma Hastanesi, 4. Kat, Ustkaynarca Pendik, Istanbul, Turkey Abbreviations: International Pediatric And Congenital Cardiac Coding (IPCCC); Atrial Septal Defect (ASD); Cardiopulmonary Bypass (CPB) Introduction with partial AV canals. In AV canal defects, aortic valve loses its After the first successful repair of an AV canal defect by C. wedged position between the left and the right AV valves. Walton Lillehei in 1955, there have been tremendous improvements in both surgical techniques and perioperative care of patients. From surgical point of view, one of the most important Nowadays early mortality after surgical repair has dropped to less morphological features of AV canal defects is the location of 3 to 4 % in many parts of the world. On the other hand, in terms the conduction system. Here, atrioventricular node is displaced of complexity, the repair of an AV canal defect could be quite inferiorly and posteriorly toward the coronary sinus due to the challenging for surgeons in some cases. When we look at Aristotle presence of an ostium primum ASD (Figure 1). With this regard, a scoring system which grades congenital cardiac procedures with special attention should be paid during surgical repair in order to regard to their complexity (simple: 1.5 to very complex: 15), prevent the development of complete AV block. surgical repair of an complete AV canal has been still classified as a comlex procedure (Aristotle score 9) [1]. Therefore, in this paper we try to summarize current surgical techniques used for repair of thisSurgical complex Anatomy pathology. and Classification of AV Canal Defects According to the International Pediatric and Congenital Cardiac Coding (IPCCC) system [2]; AV canal defects have classified into 4 main categories: Figure 1: a) complete, a. Inlet/Outlet ratio in a normal heart is equal to 1, and b) partial, Inlet/Outlet ratio in a heart with AV canal defect is less than 1 c) intermediate/transitional and b. left ventricular outflow tract in a normal heart and hearts with V canal defects. d) AV canal with ventricular imbalance. Common morphological features of AV canals are described Partial-Type: as deficiency of a portion of the inlet interventricular septum, attachment of a portion of the AV valve to the septum and equal It is a crescent shaped defect of the atrial septum distances of two AV valves to the cardiac apex (Figure 1a). Due and is also named as an ostium primum atrial septal defect (ASD). to the abnormal attachment of the anterior medial leaflet, the Anatomically, bridging leaflets attach to the ventricular septum left ventricular outflow tract seems elongated and sometimes with leaving only an interatrial connection. Despite the presence of obstructed (Figure1b). That might be more prominent in patients a single valve annulus, there are two valvular orifices. In partial AV Biomedical Journal of Scientific & Technical Research (BJSTR) 7718 Biomedical Journal of Scientific & Technical Research Volume 10- Issue 2: 2018 canal, the AV valve has usually 6 components and the commissure between the left superior and inferior leaflet is called as cleft (Figure 2). Partial AV canals have varying degrees of malformation of the left AV valve, causing varying degrees of valvular regurgitation. Figure 4: Rastelli classification of complete AV canal defects. a) Type A: The superior bridging leaflet has chordal attachments to the septum and normal arrangement of the rightb) ventricularType B: medial papillary muscle. Figure 2: Partial AV canal defect with a cleft on the left The superior bridging leaflet extends farther atrioventricular valve. into the right ventricle, being attached to an anomalous right ventricular papillary muscle arising from the trabecula Intermediate or Transitional Type: septomarginalis.c) Type C: There is a primum ASD in The free-floating superior bridging leaflet association with a restrictive VSD with this type of the defect. This extends even farther into the right ventricle and is attached to type is distinguished from complete AV canal two separate valvular Surgicalan anterior Techniques papillary muscle. orifices and the presence of a restrictive ventricular defect. Again, there is a single annulus, a common morphologic feature of all types of theAV defects. Canal with Ventricular Imbalance: For surgical repair of all types of AV canal defects, aortic and Due to the presence bicaval cannulation (metal-tipped angled cannulas) is done in a of asymmetrical commitment of the common AV valve to both standard fashion. Surgical repair of AV canal defects are usually done ventricles, one of the ventricles remains hypoplastic (Figure 3). under either normothermic or mild to moderately hypothermic Single ventricle palliation or two ventricle repair could be options cardiopulmonary bypass (CPB) and cold blood cardioplegia in in surgical treatment of these patients. our institution. Repair is standardly perfomed through the right atriotomy.Repair of Partial AV Canal Defects Repair of partial AV canal defects starts by floating of the valve with injection of saline (or cold cardioplagia solution in some centers). Injection of testing solution should be given to prevent frothing in the left heart chambers. Frothing might cause formation of microbubles within the left heart and, consequently, results in coronary embolisation and ventricular dysfunction during weaning off CPB. During testing of the valve, particular attention should be given to ensure accurate approximation of the cleft. Firstly, we start putting an approximation suture (usually 6 or 7/0 Prolene) from the free edge that is defined by the origin of the cords. Then Figure 3: AV canal defects with ventricular imbalance. multiple simple sutures are employed till the nadir of the cleft. Then, repeat testing of the valve comfirms the competency of the valve. Complete AV Canal: In case with dilated AV annulus, centrally located insufficiency With this type of morphology, there persists after closure of the cleft and it can be treated by placing are a large ostium primum atrial septal defect (ASD) and a commisuroplasty sutures. After repair of cleft, an appropriately large interventricular communication between the crest of the sized patch is sutured to the leaflet tissue between the left and interventricular septum and the inferior aspect of the common right AV valves, that necessitates special attention. Here, suturing valve. The valve might have 5 to 6 leaflets. There are always superior the patch material to the leaflet could cause laceration of the tissue, and inferior bridging leaflets. Based on the degree of bridging and leading to residual leak. The patch material is usually autologous or chordal attachment of the superior bridging leaflet, complete AV bovine pericardium (Figure 5). canal is classified into 3 types by Rastelli in 1966 (Figure 4). Cite this article: 7719 Koray Ak. Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques. Biomed J Sci&Tech Res 10(2)-2018. BJSTR. MS.ID.001930. DOI: 10.26717/ BJSTR.2018.10.001930. Biomedical Journal of Scientific & Technical Research Volume 10- Issue 2: 2018 for atrial defect autologous or bovine pericardium are used. Some authors do not prefer to divide the superior and inferior bridging leaflets during the repair of the ventricular defect. To improve the exposure, some chord attaching to the leaflet tissue away from the free margins needs to be cut. The rest of the repair is completed standardly (Figure 8). Figure 5: Closure of cleft and repair of partial AV canal defect. Repair of Complete AV Canal Defects Figure 7: The AV leaflets are sandwitched between setral crest and the patch in modified technique. Classic Single-Patch: The classic single-patch technique uses a single pericardial patch to achieve this goal. Fresh or glutaraldehyde- treated autologous pericardium is the choice of patch material with this repair. One of the most critical point of the procedure is the partition of the common valve (superior and inferior bridging leaflets) into two appropriate halves. The common AV valve is cut, and the patch is inserted in such a fashion that the lower portion of the patch closes the ventricular component of the defect, the AV valves are suspended to the patch, and the upper portion of the patch closes the atrial component (Figure 6). Figure 8: Double patch repair by division of the leaflets. Conclusion Partial AV canal defects represents approximately 25% of all AV canal defects. Although these defects show very similar physiology with secundum-type ASDs, there are known to be more complex in terms of morphology. Currently, the perioperative mortality and postoperative complete heart block rates have been reported to be minor after repair of partial AV canal defects. On the other hand, the most common indications for reoperation after surgery remain to be Figure 6: Classic single patch repair. left AV valve dysfunction (almost 10%) and left ventricular outflow tract stenosis (10 to 15 %) in the long term [3]. After repair, in Modified Single-Patch (Australian) Technique: The main addition to the fixation of the valve leaflet to the scooped-out septal crest, several inherent morphological features like abnormal cordal principle of the repair is to sandwitch the superior and inferior and papillary architecture are the main causes of LVOT stenosis. bridging leaflets between the scoop out interventricular septum For complete AV canal defects, there are many studies comparing and pericardial patch. Closure of the cleaft and the rest of the defect the impact of their above mentioned techniques on operative are theDouble same Patchas in the Technique: classic single patch repair (Figure 7).
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